lkml.org 
[lkml]   [2021]   [Jan]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFC PATCH 5/8] preempt/dynamic: Provide cond_resched() and might_resched() static calls
Date
From: "Peter Zijlstra (Intel)" <peterz@infradead.org>

Provide static calls to control cond_resched() (called in !CONFIG_PREEMPT)
and might_resched() (called in CONFIG_PREEMPT_VOLUNTARY) to that we
can override their behaviour when preempt= is overriden.

Since the default behaviour is full preemption, both their calls are
ignored when preempt= isn't passed.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
[branch might_resched() directly to __cond_resched(), only define static
calls when PREEMPT_DYNAMIC]
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
include/linux/kernel.h | 23 +++++++++++++++++++----
include/linux/sched.h | 27 ++++++++++++++++++++++++---
kernel/sched/core.c | 16 +++++++++++++---
3 files changed, 56 insertions(+), 10 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index f7902d8c1048..cfd3d349f905 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -15,7 +15,7 @@
#include <linux/typecheck.h>
#include <linux/printk.h>
#include <linux/build_bug.h>
-
+#include <linux/static_call_types.h>
#include <asm/byteorder.h>

#include <uapi/linux/kernel.h>
@@ -81,11 +81,26 @@ struct pt_regs;
struct user;

#ifdef CONFIG_PREEMPT_VOLUNTARY
-extern int _cond_resched(void);
-# define might_resched() _cond_resched()
+
+extern int __cond_resched(void);
+# define might_resched() __cond_resched()
+
+#elif defined(CONFIG_PREEMPT_DYNAMIC)
+
+extern int __cond_resched(void);
+
+DECLARE_STATIC_CALL(might_resched, __cond_resched);
+
+static __always_inline void might_resched(void)
+{
+ static_call(might_resched)();
+}
+
#else
+
# define might_resched() do { } while (0)
-#endif
+
+#endif /* CONFIG_PREEMPT_* */

#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
extern void ___might_sleep(const char *file, int line, int preempt_offset);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6e3a5eeec509..86bcb589da09 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1871,11 +1871,32 @@ static inline int test_tsk_need_resched(struct task_struct *tsk)
* value indicates whether a reschedule was done in fact.
* cond_resched_lock() will drop the spinlock before scheduling,
*/
-#ifndef CONFIG_PREEMPTION
-extern int _cond_resched(void);
+#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)
+extern int __cond_resched(void);
+
+#ifdef CONFIG_PREEMPT_DYNAMIC
+
+DECLARE_STATIC_CALL(cond_resched, __cond_resched);
+
+static __always_inline int _cond_resched(void)
+{
+ return static_call(cond_resched)();
+}
+
#else
+
+static inline int _cond_resched(void)
+{
+ return __cond_resched();
+}
+
+#endif /* CONFIG_PREEMPT_DYNAMIC */
+
+#else
+
static inline int _cond_resched(void) { return 0; }
-#endif
+
+#endif /* !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC) */

#define cond_resched() ({ \
___might_sleep(__FILE__, __LINE__, 0); \
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 15d2562118d1..d6de12b4eef2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6654,17 +6654,27 @@ SYSCALL_DEFINE0(sched_yield)
return 0;
}

-#ifndef CONFIG_PREEMPTION
-int __sched _cond_resched(void)
+#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)
+int __sched __cond_resched(void)
{
if (should_resched(0)) {
preempt_schedule_common();
return 1;
}
+#ifndef CONFIG_PREEMPT_RCU
rcu_all_qs();
+#endif
return 0;
}
-EXPORT_SYMBOL(_cond_resched);
+EXPORT_SYMBOL(__cond_resched);
+#endif
+
+#ifdef CONFIG_PREEMPT_DYNAMIC
+DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched);
+EXPORT_STATIC_CALL(cond_resched);
+
+DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched);
+EXPORT_STATIC_CALL(might_resched);
#endif

/*
--
2.25.1
\
 
 \ /
  Last update: 2021-01-18 15:17    [W:0.245 / U:1.008 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site